There's a lot of good idioms promoted in modern C++. These include RAII and elegant use of boost or STL or a std::algorithm to solve a given problem.

Just like you can write C in any language, you can certainly write C in C++. However you can write really good modern C++ code with the right subset of features. When someone does something really cool with an STL or boost construct I always get the urge to call it "pythonic" in the sense that its the canocical elegant way to do something. Is there a term like how "pythonic" is used in python to refer to C++ code written in the modern style with modern idioms?

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"Modern C++" as Nemanja Trifunovic already answered is well used, but the generic adjective for all languages is "idiomatic". So for C++ it would be "idiomatic C++". "Pythonic way" is the same as "idiomatic Python".